1. Field of the Invention
This invention relates to mandible stimulators, and, more particularly, to a mandible stimulator for producing current pulses through one or more electrode circuits having an optimum duration and an amplitude which is directly proportional to the rotational position of a potentiometer, and which includes a self-test system for flashing appropriate indicator lamps responsive to open circuit, circuit unbalance and low battery conditions.
2. Description of the Prior Art
The stimulation of muscles in the human body by electrical stimuli to provide involuntary muscular response has become a useful remedial, diagnostic and clinical technique; and in some instances, as with a cardiac stimulator, electrical stimulation has been substituted for normal electrochemical nerve signals. However, the direct, repetitive electrical stimulation of muscles by evenly timed electrical pulses fed from a simple oscillator to a single electrode pair is not practical in some instances where electronic stimulation is required. For example, in techniques producing involuntary mandibular closure, it is clinically important that contraction of the nerve fibers be effected through the motor nerves rather than by controlling the mandible by the individual stimulation of the muscles per se. Direct stimulation of the muscles is impractical due to the number of electrodes which would be required, and stimulation of the motor nerves ensures stimulation of the entire muscle complex. Also, it requires from six to eight times less electrical energy to effectively stimulate the motor nerves than would be required for direct muscle stimulation.
In the electrical stimulation of the motor nerves controlling the masticatory and facial muscles, muscularly balanced closure of the mandible may be achieved by simultaneously and evenly stimulating the motor roots of the mandibular and facial nerves on both sides of the face. If only one muscle group on one side of the face contracts, the mandible will deviate to that side as it closes. Thus, for smooth physiologic closure to occlusion, the entire muscle complex of each side of the face must contract simultaneously in group action.
If simultaneous and bilateral stimulation to produce group action of all the masticatory and facial muscles can be achieved, a number of clinical and diagnostic techniques are possible. For example, controlled stimulation may be employed to diagnose the comparative degree of relaxation or contracture of the muscle groups on each side of the face; to cause the mandible to close to the horizontal myocentric position of occlusion; to determine the vertical position of occlusion; to take denture impressions; to relax muscle spasms associated with Temporomandibular Joint Syndrome; and to reduce post-operative swelling and discoloration by causing gentle massage as the muscles contract.
One mandible stimulator which has been commonly used to perform the above described functions is disclosed in U.S. Pat. No. 3,797,500 assigned to Dr. Bernard Jankelson. Although this apparatus performs adequately under most conditions, the inventive mandible stimulator described herein includes a number of features which result in improved operating and performance characteristics. One disadvantage of this conventional mandible stimulator is that the output of the stimulator is a pulse having a manually adjustable voltage so that the currents through the electrode circuits vary depending upon such variables as the skin resistance of an individual. Since the amount of stimulus provided to the motor nerves depends upon the amount of current in the electrode circuit, and not the voltage, the amount of stimulus provided at a given stimulus setting varies greatly between individuals. Additionally, the relatively long duration pulses of the conventional mandible stimulator may produce undesirable direct stimulation of the muscles. It is generally desirable that the electrical stimuli to both left and right nerves of an individual produce equal muscle response. However, the muscles of one side may be in spasm or contracture and may require a greater stimulus amplitude for an equal balanced muscle response. A balance control is provided so the operator can make the required adjustment. In the stimulator described in U.S. Pat. No. 3,797,500 this is accomplished by separately measuring the current through each electrode circuit with a meter, a procedure which is somewhat time consuming and which may introduce inaccuracies in the measurements. In summary, although the mandible stimulator described in U.S. Pat. No. 3,797,500 can be advantageously used, additional refinements described and claimed herein greatly improve the operating efficiency and accuracy of such devices.